Implement carrying booms for hydraulic excavators and the like are normally fabricated from a plurality of steel plates secured together by a multiplicity of transverse and longitudinal welds. The plates are normally roll formed to provide a back-up ridge for the longitudinal welds (see FIG. 8 of applicant's drawings) which gives rise to various stress problems discussed in applicant's copending U.S. application Ser. No. 348,926, filed on Apr. 9, 1973 for "stress-relieved Weldment for Box Sections". Stress concentrations are particularly occasioned at a mid-portion of the boom whereat cast members are secured thereto to provide attachment means for one end of a hydraulic cylinder which is further attached to a vehicle for boom raising and lowering purposes.